abortion

gynecology
Lecture: 19.
Fifth Year Medical College.
Lecturer: Professor Layla Abdul Amir.

Abortion:
Is the expulsion of the conceptus or an attempt of expulsion the conceptus legally or illegally before the end of the 28th week of pregnancy.
Incidence ? 10 – 15% of pregnancies are lost as abortion. The common time for abortion to occur is between 7 & 13 week.
Causes of abortion:
I. Fetal causes: some fetal abnormalities make the fetus incapable of existing in the uterus.
About 25-30% of abortions in the 1st trimester is due to chromosomal abnormalities which could be due abnormal ovum, sperm or abnormal division of zygote.
Fetal causes in some cases is found that the amniotic sac not contain and embryo, a condition described as “blighted ovum” but now as an embryonic gestation.
II. Placental causes:
1) Trophoblastic abnormalities ? abnormal conceptus or abnormal division of the zygote, and this could be a partial abnormality in which there is a fetus + vesicular changes or complete abnormality in which there is no fetus.
2) Acute polyhydromnios ? excessive amniotic fluid ? quick distension of uterine cavity ? uterine contraction ? abortion.
3) Low implantation of the placenta ? bleeding ? separation of placenta ? abortion.
III. Mutual causes: the fetus usually contains both maternal and paternal antigens and may react as a graft inside the uterine cavity. So it is believed that there is an immune barrier or there is some modification in the maternal immune response during pregnancy to accommodate herself to the acceptance of the fetus, failure of this immune response will lead to abortion.
IV. Maternal causes: this include general & local causes:
A. General causes:
1) Infection: any systemic severe infection as heavy flue, typhoid fever, hepatitis will lead to abortion either due to
a) Rise in temperature.
b) Fetal infection: micro organism cross the placenta as in German measles, small pox, chicken pox, malaria, rubella, brucellosis, toxoplasmosis, cytoegalic inclusion disease. So high fever ? kill fetus ? abortion.
Infection ? stimulate uterine contraction by production of toxin by micro organism.
2) Chronic medical disease: uncontrolled hypertension, chronic renal failure, untreated T.B.
3) Iatragenic:
a) Drug ? cytotoxic, oxytoxic, ergot, prostaglandins, lead poisoning.
b) Strong purgatives ? intestinal cramps ? uterine contraction.
c) X ray therapy.
4) After laparatomy: as in appendicitis or road traffic accident.
5) Endocrine diseases: uncontrolled D.M., thyroid disease, adrenal or pituitary abnormalities.
6) Psychological factors: as shock, sudden psychological trauma ? arterial spasm to placental vessels ? abortion.
7) Malnutrition and vitamin deficiency as folic acid.
8) Manipulation.
B. Local causes:
1) Congenital Mullerian abnormalities: as in double or septate uterus, bicornuate uterus, so small uterus ? recurrent abortion and occur mostly in 2nd trimester and each pregnancy will last longer than the previous one. This type of abortion is painful abortion.
2) Retroversion of uterus: occur in 25% of females, if the uterus is mobile and it correct its position during 12-16 week of pregnancy, but if the uterus is fixed by adhesion it lead to abortion. e.g. chronic pelvic infection, endometriosis.
3) Pelvic tumour: limit expansion of uterus ? mechanical stimulation ? uterine contraction ? abortion.
As fibromyoma.
4) Cervical incompetence: dilatation of internal os of the cervix which is normally closed. Accepted diameter 1.8 cm, if > it means incompetence and this could be:
a) Congenital.
b) Acquired ? traumatic e.g. D and C, wrong application of forceps before full dilatation of cervix, cone biopsy of cervix.
Usually abortion ? painless, occur at beginning of 2nd trimester and each pregnancy last less than previous one.
5) Intrauterine adhesions.
Mechanism of abortion:
There will be a chorio decidual haemorrhage, and the blood is collected between the chorionic plate and the deciduas and this blood separate the placenta from the uterine wall. If the blood remain behind the placenta ? more separation of placenta ? abortion and this is because once the blood accumulate behind choriodecidual plate stimulate uterine contraction ? abortion.
By the 12th week the placenta is a definite structure and so abortion is similar to labour ? painful contraction + cervical dilatation. If all conceptus is expelled ? complete abortion, if retained placenta ? incomplete. If this retained placental mould by uterine contraction ? placental polyp.